Dust formulations were illuminated with ultraviolet light (2537 A) 
and the rates of decomposition were determined (1387, 1388). 
(1) RHgOH + qe eee R-Hg*+H 0 
(2) RHg* + oa ea = A Het 
Mol x 10. K(-Min) 
PMC Phenyl mercuric chloride 0.043 0. O25 1 
EMC Ethylmercuric chloride 8 0.0023 
TMC Tolylmercuric chloride 0.037 0.0151 
PMP Phenylmercuric propionate 10 0.0088 
MEMC Methoxyethylene mercuric chloride 20 0.0084 
PMA Phenyl mercuric acetate 20 0.0030 
The effect of light on fungicidal activity in a series of compounds, 
EtHgX and Ph HgX (X=anion) was dependent on the nature of X: decreasing 
activity in the order, I >Br>Cl>OQAc. In compounds RHgCl and PhHg0O,CR, 
resistance to the action of light increased as the carbon content of "'R" 
increased. In p-MeCgH,HgCl, introduction of methyl groups meta to the 
original methyl group increased light resistance; other groups decreased 
resistance. Resistance was greater in the powder state than in solution 
or suspension. Fungicidal activity of ethylmercuric compounds decreased 
markedly after 52 hours of light exposure but that of phenylmercuric com- 
pounds did not (517). 
Using arc lamps generating light of wavelengths longer than 2900A. 
The following compounds barely decomposed after the equivalent of 7 days' 
ultraviolet light: Phenylmercuric acetate, phenylmercuric chloride, 
phenylmercuric N-phenyl-p-toluene sulfamilide, and methylmercuric iodide. 
Activity of phenylmercuric dinaphthylmethane disulfonate fell markedly 
after 3 days and that of p-hydroxyphenylmercuric chloride fell slightly 
after 7 days (1291). 
241 
